Telephone headset



Jan, 13, 1925.

G. W. CARPENTER ET AL TELEPHONE HEADSET Filed June 18 1924 INVENTOR. CARPENTER L. CARI-460M k GLENN m :r & WENDELL ATTORNEY.

Patented Jan. 13, 1925.

UNITED STATES PATENT OFFICE.

GLENN W. CARPENTER AND WENDELL L. CARLSON, OF SGI-IENECTADY, NEW YORK.

TELEPHONE HEADSET.

Application filed June is, 1924. Serial No. 720,844..

To all whom it may concern:

Be it known that we, GLENN W. CARPEN- Ten and WENDELL L. CARLsoN, citizens of the United States, residing at Schenectady,

in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Telephone Headsets, of which the following is a specification.

Our invention relates broadly to flexible electric conductors and more particularly to a flexible shielded conductor for telephone headsets.

This application is a continuation in part of our application Serial No. 440,992, filed January 29, 1921.

One of the objects of our invention is to provide an electrostatic shield for electrical conductors, the shield forming an electrically conductive path surrounding the conductors and yet having a high degree of flexlbility.

Another object of our invention is to provide an electrostatic shielding for electrical conductors, consisting of a continuous shielding the electrical conductors of telephone headsets used in conjunction with sensitive multistage electron tube amplifiers where a coupling normally exists between the telephone receiver circuit and other circuits in the apparatus or external circuits. This coupling in some instances causes a detuning of the oscillatory circuit while in other instances it produces oscillations in the telephone receiver circuit which is commonly known as howling when-of an audio frequency. In the cascading of electron tubes for amplification of feeble currents the number of tubes used and degree of amplification practicable is seriously limited by the interaction of the electron tube circuits due to the inherent capacity existing between the circults and the tendency of parasitic currents to oscillate between the tube circuits. By use of our invention these capacity effects are eliminated by shielding the long connecting cords normally connected with the telephone head receivers.

Our invention has been developed particularly for service'in the United States Navy where it is important to electrostatically shield the telephone receiver circuit from the sensitive electron tube amplifier circuits in radio receiving systems. Our shield is constructed of a thin flat metallic conductor of a high degree of flexibility known as tinsel which may be helically wound over a textile thread, the resulting combination having a high degree of mechanical flexibility and yet being electrically conductive. The

metallic-tinsel and textile threads may be braided or woven in a continuous tubular weave surrounding the conductors. At the plont where the conductors are brought out through the braiding we provide a closely wound short connecting member extending from the shield which forms a stay-cord. The stay-cord terminates in a connecting device which may be secured at the head telephone receiver end of the headset to the casings of the telephone receivers. The extensions of the shield thereby serve as staycords to prevent any undue strain from being placed upon the electrical conductors at the same time that the electrostatic shield is connected to the casings of the telephone receivers. At the opposite end of the telephone cord at short closely wound extension may be formed on the electrostatic shield with a terminal at the end of the shield for making connection with a part of the electron tube circuit as fully set forth and claimed in our aforementioned application for Letters Patent.

Our invention will be more clearly understood from the following specification by reference to the accompanying drawings, in'

which:

Figure 1, is a perspective view showing the electrical conductors of our invention applied to a telephone headset; Fig. 2 is an enlarged view showing the arrangement of the conductors and the electrostatic shield surrounding the.conductors; and Fig. is a detail view illustrating the construction of the electrostatic shield.

.Referring to the drawings in detail, a telephone headset is illustrated having receiver shells designated by reference characters 33. The flexible electrical conductors are represented at 22, surrounded by the :flexible electrostatic shield 4 covered by a textile braiding 8. The conductors 2-2 are substantially insulated one from the other and comprise flexible conducting strands 1'-1 through which the currents operating the telephone headset pass. These conductors 11 have a. high degree of flexibility and low electrical resistivity. The flexible electrostatic shield 4 consists of thin flat tinsel conductors 9 helically wound over the textile threads 10. The combination of twisted conductor and thread is woven or braided together forming a continuous tubular weave of tinsel and threads around the conductors 2-2. The electrostatic shield is closely woven at the ends 55-w11ich are extended to form stay-cords. Each of the stay-cords is provided with a terminal 6 which is secured to the telephone receiver casing at 7 electrically connecting the electrostatic shield 4 with the telephone receiver casings at the same time that the stay-cord 5, being somewhat shorter than the free ends of the conductors 2-2; serves to relieve mechanical strain from the flexible conductors. At the opposite'end of the telephonecords the electrostatic shield 4 is closely wound to form an extension 12 having a terminal 14 for connection toa low potential circuit as described in our plication.

It will be observed that the combination of the helically wound tinsel conductor and the textile core forming strands which are woven or braided together providing an electrostatic shield havin a high degree'of flexibility, when encased by braiding 8 has such flexible characteristics that the conductors are substantially as flexible throughout the length of the cords as they normally would be if the shield were not provided.

While we have described our invention in a particular embodiment We desire that it be understood that modifications may be made and that no limitations are intended upon the invention other than are imposed by the scope of the appended claim.

What We claim is:

A flexible electrical conductor comprising in combination a plurality of flexible wires insulated one from the other an electrostatic shield surrounding said conductors, said shield consisting of a continuous tubular weave of copper tinsel wound over mercerized threads.

GLENN w. CARPENTER. WENDELL L. OARLSON.

aforementioned ap 

